1. Field of the Invention
The present invention relates to a manufacturing method of a semiconductor device, a semiconductor device, a communication apparatus, and a semiconductor laser. More particularly, the invention relates to a manufacturing method of a semiconductor device that includes a semiconductor laminated structure in its structure, a semiconductor device, a communication apparatus, and a semiconductor laser.
2. Description of the Related Art
Semiconductor optical devices include optical devices that perform electricity-light conversion/light-electricity conversion, such as light emitting devices and light receiving devices, and optical devices that transmit optical signals, such as optical waveguides, optical switches, isolators, and photonic crystals.
The light emitting devices such as semiconductor lasers and light-emitting diodes, of the optical devices that perform the electricity-light conversion/light-electricity conversion, each include a semiconductor laminated structure constituted of a plurality of semiconductor layers including an active layer of a semiconductor hetero structure or a quantum well structure. These light emitting devices utilize the action of radiation recombination in the semiconductor laminated structure to perform the electricity-light conversion.
The light receiving devices each similarly include a semiconductor laminated structure constituted of a plurality of semiconductor layers. The light receiving devices each utilize the action of light absorption in a certain semiconductor layer in the semiconductor laminated structure to perform the light-electricity conversion.
The optical devices that perform the transmission of the optical signals each include, depending on their types, a semiconductor laminated structure constituted of a plurality of semiconductor layers having predetermined refractive indices (or a plurality of semiconductor layers that include a semiconductor layer having a variable refractive index by an electrooptic effect). The optical devices that perform the transmission of the optical signals each perform desired optical-signal transmission utilizing a difference between refractive indices of the plurality of semiconductor layers.
While the optical devices described above are mainly constituted of the semiconductor laminated structures, their manufacturing methods sometimes include a process for changing a physical property of a predetermined semiconductor layer in the semiconductor laminated structure.
For example, when the optical device is a semiconductor laser, a window region may be formed on an emission facet for getting laser light generated by resonating light generated by radiation recombination to the outside. The emission facet of the semiconductor laser may be degraded by high-density light absorption, and this may cause catastrophic optical damage (COD). Therefore, in the semiconductor laser formed with the window region, absorption of emitted light at the position of the emission facet is reduced by increasing the bandgap of the semiconductor of the semiconductor laminated structure at that position.
To form such a window region, for example, in a GaAs semiconductor laser, a dielectric film having an effect of promoting diffusion of Ga of a semiconductor laminated structure corresponding to the window region is formed on laminated layers of the semiconductor laminated structure, as described in Japanese Patent Application Laid-open No. H7-122816. The semiconductor laminated structure is then heat-treated, thereby disordering a predetermined semiconductor layer in the semiconductor laminated structure corresponding to the window region, and changing a physical property value of the semiconductor layer. That is, a process of increasing a bandgap is performed. This method is called an impurity free vacancy disordering (IFVD) method.